Physical modeling of an underground roadway excavation in vertically stratified rock using infrared thermography

Physical modeling of an underground roadway excavation in vertically stratified rock using infrared thermography

Manchao He ^a,b,*, Xuena Jia ^a,b, Weili Gong ^a,b, Lohrasb Faramarzi ^c

^a State Key Laboratory for Geomechanics & Deep Underground Engineering, Beijing 100083, China

^b School of Mechanics and Civil Engineering, China University of Mining & Technology, Beijing 100083, China

^c Department of Mining Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran

Doi.10.1016/j.ijrmms.2010.06.020

Introduction

As a result, new physical modeling method with large-scale physical model, along with the state-of-the art measuring techniques, needs to be introduced into the laboratory test. Systematic experimental studies have been carried out at the State Key Laboratory for Geomechanics and Deep Underground Engineering at the China University of Mining & Technology Beijing (CUMTB), on the rock responses of the underground openings under excavation or in operation at great depth. A new physical modeling method, the so-called ‘‘physically finite elementary slab assemblage (PFESA)’’ has been proposed for the construction of laboratory physical model in large scale, modeling the creation and operation of a roadway tunnel in the stratified rock masses [21,22]. The PFESA method uses a specimen-sized rectangular plate, i.e. the ‘‘elementary slab’’, made of artificial materials (also referred to as ‘‘similarity materials’’ hereafter), simulating real rocks in terms of physical and mechanical properties. Rock strata at different inclinations can be simulated by making layers with these elementary slabs at specified orientations. Infrared (IR) thermography has been extensively used as a nondestructive and noncontact technique to inspect cracks or defects inside materials [23], detecting disbands between coating and substrate of coated materials [24] and examining the progressive failure of concrete and rock specimens [25], as well as describing the dynamical process of turbulence by its spectral-frequency characteristics [26], for example. IR thermography, together with such image processing procedures as feature extraction and frequency-spectral analysis, were used to visualization and characterization of the mechanical and structural responses of rockmasses over the excavation impact or the external loading in real-time and over the entire field [21,22]. Up to now, experimental works conducted at CUMTB involve the construction of the large-scale PFESA models imitating the geological strata at the inclination angles of 0, 15, 30, 45, 60, 90 degrees, respectively, the rock responses to the roadway tunnel excavation in these models, as well as the stability of the excavated roadways under high confining stresses similar to that of the deep mining. The physical modeling works on roadway tunnel in the geologically horizontal strata under excavation [22] and in operation [21] were reported previously. The roadway preexcavated in the horizontal strata deformed and collapsed under a plane loading state, and the stress path was designed to simulate high confining stresses in deep mining ranging from 350 to 2600 m, its detailed documentation can be found in literature [21]. The IR characterization of the roadway tunnel excavation itself in the geologically horizontal strata, reported in literature [22], and will be introduced in brief in this letter for comparison with the IR characterization of the roadway excavation in the geologically vertical strata which is the main subject presented in this letter.